JP3489107B2 - Eye movement detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called sclera in which the eye movement of a subject is measured based on the difference in reflectance between the iris (cornea) and the white (sclera) of the eyeball. The present invention relates to a reflection type eye movement detecting device. 2. Description of the Related Art Conventionally, this type of eye movement detecting device is particularly effective when trying to measure eye movement in the field of psychological experiments and medical treatments such as psychology, engineering, and medicine. The same applicant has disclosed a specific configuration in Japanese Patent Laid-Open Publication No. 1-268538 and the like. FIG. 4 illustrates the principle of detecting eye movement. In FIG. 4, reference numeral 1 denotes an eyeball of a subject,
The eyeball 1 is provided with a sensor 2 for detecting horizontal eye movement and a sensor 3 for detecting vertical eye movement in which three elements are juxtaposed. The sensor 2 includes an infrared LED 4 that is a light emitting element that irradiates infrared light to a black eye positioned at the center of the surface of the eyeball 1, and a pair of right and left light receiving elements that receive light reflected by the infrared LED 4 from the surface of the eyeball 1. And a photodiode 5. The output of each photodiode 5 is input to a differential amplifier 6 and converted into electric signal information indicating a horizontal eyeball position. Therefore, when the subject is looking straight ahead, that is, when the iris is at the center of the eyeball 1, the output of the differential amplifier 6 becomes substantially zero. On the other hand, the sensor 3 includes an infrared LED 7 which emits infrared light toward the lower edge of the surface of the eyeball 1 and a light receiving element which receives light reflected by the infrared LED 7 from the surface of the eyeball 1. It comprises a pair of right and left photodiodes 8. The output of each photodiode 8 is a summing amplifier 9
And is converted into electrical signal information indicating the vertical eyeball position. Accordingly, when the eyeball 1 faces downward, the area of the iris increases and the amount of light reflected from the eyeball 1 decreases, and conversely, the eyeball 1
Turns upward, the area of the white of the eye increases, and the amount of light reflected from the eyeball 1 increases. As described above, the eye movement of the subject is measured based on the signal information from the differential amplifier 6 and the addition amplifier 9 using the difference in the reflectance between the black eye and the white eye of the eyeball 1. Next, the installation locations of the sensors 2 and 3 will be described with reference to FIG. In the figure, 1 is an eyeball, 2, 3
Is a unitized sensor. In the explanatory diagram of FIG. 4, a state in which the eyeball is divided into right and left is shown. However, in actuality, the sensor 2 and the sensor 3 are arranged vertically on the same eyeball 1. To detect eye movement with the highest accuracy,
It is preferable to install the sensors 2 and 3 in front of the eyeball 1. However, since the sensors 2 and 3 obstruct the visual field of the subject, generally,
As shown in the figure, from the lower part of the eyeball 1 toward the eyeball 1, the distance L from the sensors 2 and 3 to the surface of the eyeball 1 is 15 mm, and the angle α from the front direction of the eye is 20 ° to 30 °. You have set. However, when the subject wears spectacles, the spectacle lens A is inserted as shown by a broken line in the figure, and the distance L between the sensors 2 and 3 and the eyeball 1 is often 15 mm or more. In addition, the irradiation light and the reflected light are applied to the spectacle lens A twice.
, The amount of light detected by the photodiode 5 or the photodiode 8 is considerably attenuated. In the above prior art, since the amount of light emitted from each of the light-emitting LEDs 4 and 7 is always constant, for example, a subject such as a young person having a high reflectance of the surface of the eyeball 1 has a high reflectance. In some cases, the amount of light reflected from the eyeball 1 becomes excessive, and the amount of light detected by the photodiode 5 or the photodiode 8 is saturated. On the other hand, a spectacle lens A is inserted between the eyeball 1 and the sensor 2, such as an elderly person, whose reflectance is low on the surface of the eyeball 1, or a spectacle wearer, and the amount of reflected light from the eyeball 1 is extremely high. In the case where the number of the eyeball movements decreases, the detection output from the photodiode 5 or the photodiode 8 decreases, and there is a problem that the eyeball movement cannot be accurately detected. For this reason, the detection range must be narrowed for the former young person, or the experiment must be performed at the expense of accuracy or SNR (signal-to-noise ratio) for the latter elderly person or eye wearer. It was the current situation. In particular, as a countermeasure in the latter case, it is conceivable to increase the amount of light emitted from each of the light-emitting LEDs 4 and 7, but when considering the effect on the eyeball 1, the amount of light applied to the eyeball 1 is kept to a minimum. Action is required. However, there is no device that takes such a point into consideration. [0007] The present invention has been made in view of the above problems, minimize the impact on the eye, yet when the eye movement for any given subject can be detected accurately co
Another object of the present invention is to provide an eye-movement detecting device that can further improve the accuracy of correcting the amount of reflected light . According to the present invention, there is provided a light-emitting element for irradiating infrared light to a subject's eyeball surface, and a pair of light-receiving elements for receiving light reflected from the subject's eyeball surface, In an eyeball movement detection device that measures the eyeball movement of a subject by the difference in reflectance between the black eye and the white eye of the eyeball, a gaze target that the subject gazes at, and the output of each of the light receiving elements is added and the vertical
An addition amplifier that converts the information into electric signal information indicating an eyeball position,
From the summing amplifier when gazing at the gaze target
The irradiation light amount of the light emitting element based on the addition result is obtained and a control means for variably controlling. According to the above arrangement, the amount of light emitted from the light emitting element increases for a subject whose amount of reflected light from the eyeball is small, and the amount of light reflected from the eyeball increases for a subject whose amount of reflected light from the eyeball is small.
The amount of light emitted from the light emitting element is reduced, and the accuracy of detecting eye movement is improved. In addition, since the amount of light emitted from the light emitting element varies depending on the amount of light reflected from the eyeball of the subject, the amount of light emitted from the light emitting element can be reduced for subjects who can sufficiently measure even the originally small amount of light. Can be minimized. In addition, since the operation of correcting the amount of reflected light can be performed at the time of the calibration operation for matching the point actually observed by the subject with the detection position of the apparatus, the calibration time does not become long. Also, a pair of receivers for detecting vertical eye movements are provided.
Each output from the optical element is added, and the output is generated based on the addition result.
Since the irradiation light quantity of the optical element is variably controlled,
The vertical eye movement that reflects the amount of light reflected from the eye
Using detection output to further improve the accuracy of reflected light correction
Can be. An embodiment of the present invention will be described below in detail with reference to FIGS. The basic operation principle of the device is the same as that shown in FIGS. FIG. 1 shows a main block diagram of an apparatus according to the present invention. In the figure, reference numeral 3 denotes the aforementioned sensor for detecting the eye movement in the vertical direction. The sensor 3 includes an infrared LED 7 that irradiates infrared light toward the lower edge of the surface of the eyeball 1 and a pair of photodiodes 8 that receives light reflected from the surface of the eyeball 1 when the infrared LED 7 irradiates. I have. The output of the photodiode 8 is converted into an electric signal indicating vertical eye movement by the light receiving unit 11 including the addition amplifier 9 and the like. The electric signal from the light receiving unit 11 is
The data is also output to the CPU 12 as control means. Reference numeral 13 denotes a gazing target such as a visible LED which is gazed at by a subject disposed in the center of the calibration board 21 shown in FIG. The gaze target 13 is provided to match the position actually observed by the subject with the detection position of the device. Reference numeral 14 denotes an alarm device such as a buzzer. The lighting of the gaze target 13 and the sounding of the alarm device 14 are controlled by the CPU 12. The CPU 12 also determines the amount of light emitted from the light emitting LED 7 based on the output of the photodiode 8 passing through the light receiving unit 11 when the subject is gazing at the gaze target 13 so that the eye movement can be accurately detected. And a variable irradiation light amount control means (not shown) for variably controlling the irradiation light amount within a range that does not affect the light amount. Reference numeral 15 denotes a light emission control unit that drives the irradiation light amount of the light emitting LED 7 under the control of the CPU 12. Although not shown in FIG. 1, the sensor 2
The light-emitting LED 4 is also connected to the light-emission control unit 15, and the irradiation light amount is variably controlled by the CPU 12 together with the light-emitting LED 7. Further, the output from the photodiode 5 of the sensor 2 is converted into electric signal information indicating the horizontal eyeball position via the differential amplifier 6. Next, the operation of the above configuration will be specifically described. First, the operating principle will be disclosed.
In order to variably set the irradiation light amounts of D4 and D7 to optimal values,
It is necessary to measure the amount of reflected light on the surface of the eyeball 1 when the eyeball 1 is irradiated with the reference irradiation light amount. In this case, since the detection principle of the eyeball movement itself detects a change in the amount of reflected light, the amount of reflected light greatly changes depending on the position of the eyeball 1 of the subject. Therefore, it is necessary to determine the position of the eyeball 1 serving as a reference. However, the position of the eyeball 1 gazing in the front direction where the amount of reflected light from the eyeball 1 is most stable is considered as a reference. That is, when correcting the amount of reflected light, the CPU 12 controls the lighting of the gaze target 13 at the position shown in FIG. 2 and arranges this at the front of the subject to make the subject gaze. However, as described above with reference to the principle of detecting the eye movement with reference to FIG. 4, when the subject is gazing in the front direction, the detection output of the eye movement in the horizontal direction is output from both photodiodes 5. Since the output difference of
The amount of reflected light is no longer reflected. On the other hand, the detection output of the eye movement in the vertical direction is output from both photodiodes 8.
Are obtained by substantially evenly adding the outputs of the above, and it is considered that the reflected light amount is well reflected. Therefore, in the present embodiment, the output of the sensor 3 for detecting the vertical eye movement is utilized, and this output is converted into an electric signal indicating the vertical eye movement by the light receiving section 11 provided with the addition amplifier 9. And outputs the same to the CPU 12 to measure the amount of reflected light from the eyeball 1. The amount of reflected light input at this time is defined as Ri. On the other hand, it is assumed that a pre-measurement is performed in advance by an experiment or the like, and as a result, a preferable reflected light amount at which standard accuracy can be obtained is Rth. The CPU 12 calculates the actual reflected light amount R
The ratio G between i and the preferred amount of reflected light Rth, that is, The light emission control unit 15 is controlled so that the irradiation light amount of the light emitting LEDs 4 and 7 becomes G times. Specifically, the actual reflected light amount Ri is smaller than the preferred reflected light amount Rth. If the light emitting LEDs 4 and 7
Is increased, while the actual reflected light amount Ri is larger than the preferred reflected light amount Rth. If the light emitting LEDs 4 and 7
To reduce the amount of irradiation. The CPU 12 variably controls the irradiation light amount of the light-emitting LEDs 4 and 7 so that the reflection light amount Ri from the eyeball 1 becomes a preferable reflection light amount Rth, and thereafter, the eye movement is measured by the preferable reflection light amount Rth. In this embodiment, assuming that the normal reflected light amount obtained when the subject wears the standard spectacle lens A is Rs, the CPU 12 determines a value significantly smaller than the reflected light amount Rs, for example, the reflected light amount. The half value of Rs is stored as the minimum reflected light amount R1. And CPU12
When the reflected light amount Ri obtained when the subject gazes at the gaze target 13 is smaller than the minimum reflected light amount R1, the mounting position of the sensor 3 is rather than the decrease in the reflected light amount due to the effect of the glasses. Is judged to be defective, the alarm device 14 is sounded to give an alarm to the wearer, and the light emission control unit 15 is controlled so that the light emission from the light emitting LEDs 4 and 7 is not changed with the initial light amount. This can eliminate the problem that the amount of light applied to the eyeball 1 is unnecessarily increased and the SNR is reduced. The present apparatus also has the advantage that the operation of correcting the amount of reflected light by the CPU 12 need not be performed independently. This is because, in such an eye movement detection method, the calibration board 21 having a plurality of points as shown in FIG. This is because it is necessary to perform a calibration operation for matching the detection position of the apparatus with the detection position of the apparatus. That is, if the subject performs the above-described operation of correcting the amount of reflected light while the subject is gazing at the gaze target 13 at the center, there is no fear that the calibration time is unnecessarily long. As described above, the eye-movement detecting device of the embodiment described above uses the light-emitting LEDs 4 and 7 based on the gaze target 13 that the subject gazes at and the output from the photodiode 8 when the gaze target 13 is being gazed at. CPU variably controls the amount of irradiation of light
12, the irradiation light amount of the light-emitting LEDs 4 and 7 is increased for a subject whose reflected light amount from the eyeball 1 is small, so that the detection accuracy of the eye movement is improved and the SNR is improved.
Also improve. Conversely, for a subject whose amount of reflected light from the eyeball 1 is large, the amount of light emitted from the light-emitting LEDs 4 and 7 is reduced, so that the problem that the output of the photodiode 5 or the photodiode 8 is saturated by a large movement of the eyeball 1 can be eliminated. In addition, the minimum necessary dynamic range can be ensured, and the detection range can be expanded to improve the accuracy of detecting the eye movement. In this case, the amount of light emitted from the light-emitting LEDs 4 and 7 varies according to the amount of light reflected from the eyeball 1 of the subject.
For a subject who can sufficiently measure even the originally small amount of irradiation light, the irradiation light amount of the light-emitting LEDs 4 and 7 is reduced,
Impact on the environment can be minimized. Moreover, since the operation of correcting the amount of reflected light can be performed at the time of the calibration operation for matching the point actually observed by the subject with the detection position of the apparatus, the calibration time does not become long. In the above configuration, the outputs from the pair of light receiving elements for detecting the eye movement in the vertical direction, ie, the photodiodes 8, are added, and the CPU 12 determines the amount of light emitted from the light emitting elements, ie, the light emitting LEDs 4, 7, based on the addition result. It is preferable to configure so as to perform variable control. This is due to the fact that the detection output of the eye movement in the vertical direction reflects the amount of light reflected from the eyeball 1 well.
The correction accuracy of the amount of reflected light by the PU 12 can be further improved. It is preferable that the fixation target 13 is provided at a position substantially facing the front of the eyeball 1. In this case, the amount of light reflected from the eyeball 1 is stabilized, and the accuracy is improved.
7 can be changed to a preferable value. In the above configuration, even if the output of the photodiode 8 at the time of correcting the amount of reflected light is extremely reduced due to a defective mounting position of the sensor 3, the correction is performed without knowing this, and the eye movement can be accurately determined. The problem that it cannot be detected is caused. In this case, the light emitting LED
There is a possibility that the irradiation light amounts 4 and 7 may increase to a level that is not desirable for the eyeball 1. Therefore, in order to solve such a problem, the present apparatus further includes a notifying unit that notifies when the output of the photodiode 8 when the gaze target 13 is gazing is equal to or less than a predetermined value, that is, an alarm device 14. It is possible to notify the defect of the mounting position of the sensor 3 in advance, and in this case, the light emission L
Since the irradiation from the EDs 4 and 7 does not change with the initial light amount, it is possible to prevent the irradiation of the subject's eyeball 1 from being excessively performed. The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in the embodiment, the reflected light amount from the eyeball 1 at the time of gazing is measured using the output from both photodiodes 8 of the sensor 3 that detects the eye movement in the vertical direction. One input of the summing amplifier 9, that is, only one output of the photodiode 5 or the photodiode 8 may be used.
Further, it is of course possible to measure the amount of reflected light by combining a plurality of outputs of the photodiodes 5 and 8. According to the present invention, there is provided a light-emitting element for irradiating infrared light to the eyeball surface of a subject, and a pair of light-receiving elements for receiving light reflected from the eyeball surface of the subject. In an eye movement detection device that measures the eye movement of a subject by a difference in reflectance from the white eye, a gaze target that the subject gazes at and the output of each of the light receiving elements are added to indicate the vertical eye position.
An addition amplifier for converting the signal into electric signal information, and control means for variably controlling the irradiation light amount of the light emitting element based on the addition result from the addition amplifier when the fixation target is gazing.
In addition to minimizing the effect on the eyeball, it is possible to accurately detect the eyeball movement for any subject and to compensate for the amount of reflected light.
The accuracy can be further improved . Also, there is an effect that the calibration time is not unnecessarily long.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an apparatus showing one embodiment of the present invention. FIG. 2 is a front view of the calibration board showing the position of the gaze target; FIG. 3 is a front view of a calibration board used when calibrating the eye movement apparatus. FIG. 4 is a schematic explanatory view showing a general principle of detecting eye movement. FIG. 5 is a schematic explanatory view showing a preferred installation position of the sensor. [Description of Signs] 4,7 Light-emitting LED (light-emitting element) 5,8 Photodiode (light-receiving element) 9 Addition amplifier 12 CPU (control means) 13 Gaze target

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kunihiko Ishiyama 1-10-11 Kinuta, Setagaya-ku, Tokyo Human Broadcasting Research Institute Human Science Department, Japan Broadcasting Corporation (72) Inventor Akio Takei Kamiikedaizo, Ota-ku, Tokyo No. 29-1 (56) References JP-A-1-268538 (JP, A) JP-A-3-109028 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B3 / 10-3/18

Claims (1)

(57) a light emitting element for irradiating the Patent Claims 1 The infrared light on the ocular surface of the subject, one for receiving reflected light from the eyeball surface of the subject
And a pair of light receiving elements, the eye movement detecting device for measuring eye movement of the subject due to the difference in reflectance between the eye of the iris and whites, the gaze optotype the subject is gazing, each receiving
The electrical signal information indicating the vertical eye position is obtained by adding the outputs of the optical elements.
Eyeball to the summing amplifier that converts the broadcast, characterized in that a control means for variably controlling the light quantity of the light emitting element based on the addition result from the summing amplifier when gazing the gaze optotypes Motion detection device.